1. Field of the Invention
The present invention relates to data communications and particularly to a system and method for establishing bidirectional optical communications between associated data units.
2. Description of the Prior Art
Many different separate systems, subsystems or units have-been developed in the electronics field for processing and handling data. Such separate units frequently must be temporarily connected or coupled to other data processing systems or units for exchanging data therebetween. This is particularly true when one unit is portable and the other unit is fixed in position.
Typically, such units are temporarily coupled together by means of electrical connections. Electrical connections between separable units can be accomplished in a number of ways. One conventional way is to have conductive spring fingers on one unit pressing against conductive strips along the edge of the other unit. Another way is to have electrical contacts on one unit moved against the other unit to mate with conductive strips on the other unit when it is in place. Other ways are by means of capacitive or inductive coupling between closely positioned conductors of the two units or by the reception by one unit of radio frequency emissions from the other unit.
The above-described different types of electrical connections for temporarily coupling two units together can suffer from one or more of the following problems:
(1) intermittent contact due to wear or contamination, PA0 (2) contact corrosion, PA0 (3) physical damage, PA0 (4) improper or incomplete physical coupling between the two units, and PA0 (5) excess power required in one of the units.
By optically, rather than electrically, coupling the two units together the problems associated with wear and poor electrical contact are eliminated. Also, the position of one unit with respect to the other unit is far less critical with optical coupling than with electrical coupling. In addition, there is no wear or damage with repeated use.
Optical coupling is particularly advantageous for the transfer of data between the two units when the units are frequently connected and disconnected, when good alignment between units or careful physical insertion or connection cannot be guaranteed, when vibration or mechanical stress would destroy contacts, when environmental conditions would erode conventional contacts and when minimizing the power consumption of one unit for optical communication is critical.
Other practical uses for optical coupling exist where communication is needed between two units sitting side-by-side or even between two circuit boards in adjacent sockets, and also where the units are physically separated by a relatively long distance.
The background art known to the applicants at the time of the filing of this application is as follows:
U.S. Pat. No. 3,377,616, Vehicle Identification System, by J. H. Auer, Jr.;
U.S. Pat. No. 3,630,015, Light Transformation Device, by K. Lehovec;
U.S. Pat. No. 3,705,986, Optical Data Transmission System, by R. W. Sanders et al;
U.S. Pat. No. 4,063,083, Data Communication Systems Using Light Coupled Interfaces; by W. T. Cathey et al;
U.S. Pat. No. 4,234,969, Bidirectional Optical Coupler For A Data Processing System, by A. J. Singh; and
U.S. Pat. No. 4,310,754, Communication Means With Transducer Physically Spaced From Interior Wall of Secure Housing, by F. T. Check, Jr.